Delete Geometry inside a simulation zone with the radius expanding or shrinking

[Lawrence]

Hi everyone, in a previous post, I asked for help to create a delete geometry node using a boolean probability node in a simulation zone and got the results I wanted, but have been trying to add onto that and try to make it so that when the probability is adjusted, either the point appears using the delete geometry node and radius expands to the radius size you want or shrinks down the radius size until 0, and then deletes the geometry.
I have tried multiple things and can not get it to work the way I want it to, would anybody have an idea how to do this?
Thank you for any responses

Here is my previous post

Delete Geometry inside a simulation zone

Hey everyone, having an issue trying to figure this out, is there a way to use a delete geometry node to reduce and respawn points inside of a simulation zone? I want the animation to have the points gradually appear over time, if I use it outside of the simulation, it does nothing to the simulation I am using but I can set the number of points I start off with, or if it’s in a simulation, it reduces the point count constantly until they are all gone and can’t get them back. If this isn’t possi…

Here is the code that works from KDLynch using the probability boolean with the delete geometry node

Here are my failed attempts to try to get it to work, obviously they never worked and it’s a complete mess, but thought I’d show you I attempted it haha I just can’t get my head around this

[zeroskilz]

@Lawrence

point appears using the delete geometry node

Huh? If you delete a point its gone.

@Lawrence

radius expands to the radius size you want or shrinks down the radius size until 0, and then deletes the geometry.

That is possible:

The Random Float is the Target Radius. Add a fraction of the difference between the Target Radius and the Current Radius to the Radius on each frame. Negative Radiuses are “False” so Not that are the points to delete.

I understand what KD is doing with the 2 Geometry branches - essentially by keeping the other Geometry branch you’re keeping the indices constant so the Random Value nodes will behave consistently… an alternative I’m presenting here is to just capture the initial indices and feed those into the Random Value nodes.

Good luck.

[Lawrence]

Thank you for the reply, it is not what I was hoping to accomplish but definitely thankful for the response, and seeing the code the way you have done it helped, I tried to combine both but can not make it work, I feel like it might not be possible right? If its not i am happy to continue without it, but it would have looked far cleaner having the points reduce into a delete and expand back.

Again, thank you for replying!

[KDLynch (Kelly Lynch)]

Hi Lawrence,

If i understand correctly, then the boolean probability won’t work for you… as that is just on/off … no fuzziness between the two to give you ‘spacetime’ to grow or shrink in.

you’d want to instead compare each point to a probability factor range… if less than, the point is gone. if greater than the range, the point is full size, and anything in between is where you’d grow or shrink between 0 and whatever the max size of the point is.

point-cloud-probs-shrinkydinks.blend (1011.1 KB)

the posted example only allows for one (max) size for all points, but could be reworked to allow each point to have it’s own max size (you’d need a second named attribute to store the points max size in, and then that would need to feed the formula to calculate the size in)

Zero uses probably a better method for dealing with the three point groups… i started by deleting those ‘too small/beneath threshold’ and then splitting those that are at max size, and those growing. his approach went the other way, not differentiating between growing/max size, and .then. deleting anything that had no point radius.

[Lawrence]

You are amazing, this is exactly the outcome I wanted, and it looks amazing, I can’t believe you have this working, very happy to not use a probability node, but thought that was the best solution to randomize the delete of geometry
I really hope I can get as good at geometry nodes as you someday!
Thank you again!!! This is so beautiful!